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coreaudio: The default SDL audio device now tracks the system output …
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…default.

So if you go into System Preferences on a MacBook and toggle between a pair of
connected bluetooth headphones and built-in internal speakers, SDL will
switch the device it is playing sound through, to match this setting, on the
fly.

Likewise if the default output device is a USB thing and is unplugged; as the
default device changes at the system level, SDL will pick this up and carry
on with the new default. This is different from our unplug detection for
specific devices, as in those cases we want to send the app a disconnect
notification, instead of migrating transparently as we now do for default
devices.

Note that this should also work for capture devices; if the device changes,
SDL will start recording from the new default.

Fixes Bugzilla #4851.
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@icculus
icculus committed Mar 29, 2020
1 parent 46bb47c commit 55b4f18
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Showing 2 changed files with 118 additions and 27 deletions.
2 changes: 2 additions & 0 deletions src/audio/coreaudio/SDL_coreaudio.h
View file
Expand Up @@ -47,6 +47,7 @@ struct SDL_PrivateAudioData
{
SDL_Thread *thread;
AudioQueueRef audioQueue;
int numAudioBuffers;
AudioQueueBufferRef *audioBuffer;
void *buffer;
UInt32 bufferOffset;
Expand All @@ -57,6 +58,7 @@ struct SDL_PrivateAudioData
SDL_atomic_t shutdown;
#if MACOSX_COREAUDIO
AudioDeviceID deviceID;
SDL_atomic_t device_change_flag;
#else
SDL_bool interrupted;
CFTypeRef interruption_listener;
Expand Down
143 changes: 116 additions & 27 deletions src/audio/coreaudio/SDL_coreaudio.m
View file
Expand Up @@ -34,11 +34,21 @@

#define DEBUG_COREAUDIO 0

#define CHECK_RESULT(msg) \
if (result != noErr) { \
SDL_SetError("CoreAudio error (%s): %d", msg, (int) result); \
return 0; \
}
#if DEBUG_COREAUDIO
#define CHECK_RESULT(msg) \
if (result != noErr) { \
printf("COREAUDIO: Got error %d from '%s'!\n", (int) result, msg); \
SDL_SetError("CoreAudio error (%s): %d", msg, (int) result); \
return 0; \
}
#else
#define CHECK_RESULT(msg) \
if (result != noErr) { \
SDL_SetError("CoreAudio error (%s): %d", msg, (int) result); \
return 0; \
}
#endif


#if MACOSX_COREAUDIO
static const AudioObjectPropertyAddress devlist_address = {
Expand Down Expand Up @@ -441,7 +451,7 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
if (!SDL_AtomicGet(&this->enabled) || SDL_AtomicGet(&this->paused)) {
/* Supply silence if audio is not enabled or paused */
SDL_memset(inBuffer->mAudioData, this->spec.silence, inBuffer->mAudioDataBytesCapacity);
} else if (this->stream ) {
} else if (this->stream) {
UInt32 remaining = inBuffer->mAudioDataBytesCapacity;
Uint8 *ptr = (Uint8 *) inBuffer->mAudioData;

Expand Down Expand Up @@ -576,6 +586,18 @@ static BOOL update_audio_session(_THIS, SDL_bool open)

return 0;
}

/* macOS calls this when the default device changed (if we have a default device open). */
static OSStatus
default_device_changed(AudioObjectID inObjectID, UInt32 inNumberAddresses, const AudioObjectPropertyAddress *inAddresses, void *inUserData)
{
SDL_AudioDevice *this = (SDL_AudioDevice *) inUserData;
#if DEBUG_COREAUDIO
printf("COREAUDIO: default device changed for SDL audio device %p!\n", this);
#endif
SDL_AtomicSet(&this->hidden->device_change_flag, 1); /* let the audioqueue thread pick up on this when safe to do so. */
return noErr;
}
#endif

static void
Expand All @@ -586,8 +608,9 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
/* !!! FIXME: what does iOS do when a bluetooth audio device vanishes? Headphones unplugged? */
/* !!! FIXME: (we only do a "default" device on iOS right now...can we do more?) */
#if MACOSX_COREAUDIO
/* Fire a callback if the device stops being "alive" (disconnected, etc). */
AudioObjectRemovePropertyListener(this->hidden->deviceID, &alive_address, device_unplugged, this);
if (this->handle != NULL) { /* we don't register this listener for default devices. */
AudioObjectRemovePropertyListener(this->hidden->deviceID, &alive_address, device_unplugged, this);
}
#endif

if (iscapture) {
Expand Down Expand Up @@ -676,6 +699,26 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
this->hidden->deviceID = devid;
return 1;
}

static int
assign_device_to_audioqueue(_THIS)
{
const AudioObjectPropertyAddress prop = {
kAudioDevicePropertyDeviceUID,
this->iscapture ? kAudioDevicePropertyScopeInput : kAudioDevicePropertyScopeOutput,
kAudioObjectPropertyElementMaster
};

OSStatus result;
CFStringRef devuid;
UInt32 devuidsize = sizeof (devuid);
result = AudioObjectGetPropertyData(this->hidden->deviceID, &prop, 0, NULL, &devuidsize, &devuid);
CHECK_RESULT("AudioObjectGetPropertyData (kAudioDevicePropertyDeviceUID)");
result = AudioQueueSetProperty(this->hidden->audioQueue, kAudioQueueProperty_CurrentDevice, &devuid, devuidsize);
CHECK_RESULT("AudioQueueSetProperty (kAudioQueueProperty_CurrentDevice)");

return 1;
}
#endif

static int
Expand All @@ -696,26 +739,21 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
CHECK_RESULT("AudioQueueNewOutput");
}

#if MACOSX_COREAUDIO
{
const AudioObjectPropertyAddress prop = {
kAudioDevicePropertyDeviceUID,
iscapture ? kAudioDevicePropertyScopeInput : kAudioDevicePropertyScopeOutput,
kAudioObjectPropertyElementMaster
};
CFStringRef devuid;
UInt32 devuidsize = sizeof (devuid);
result = AudioObjectGetPropertyData(this->hidden->deviceID, &prop, 0, NULL, &devuidsize, &devuid);
CHECK_RESULT("AudioObjectGetPropertyData (kAudioDevicePropertyDeviceUID)");
result = AudioQueueSetProperty(this->hidden->audioQueue, kAudioQueueProperty_CurrentDevice, &devuid, devuidsize);
CHECK_RESULT("AudioQueueSetProperty (kAudioQueueProperty_CurrentDevice)");
#if MACOSX_COREAUDIO
if (!assign_device_to_audioqueue(this)) {
return 0;
}

/* !!! FIXME: what does iOS do when a bluetooth audio device vanishes? Headphones unplugged? */
/* !!! FIXME: (we only do a "default" device on iOS right now...can we do more?) */
/* Fire a callback if the device stops being "alive" (disconnected, etc). */
AudioObjectAddPropertyListener(this->hidden->deviceID, &alive_address, device_unplugged, this);
}
#endif
/* only listen for unplugging on specific devices, not the default device, as that should
switch to a different device (or hang out silently if there _is_ no other device). */
if (this->handle != NULL) {
/* !!! FIXME: what does iOS do when a bluetooth audio device vanishes? Headphones unplugged? */
/* !!! FIXME: (we only do a "default" device on iOS right now...can we do more?) */
/* Fire a callback if the device stops being "alive" (disconnected, etc). */
/* If this fails, oh well, we won't notice a device had an extraordinary event take place. */
AudioObjectAddPropertyListener(this->hidden->deviceID, &alive_address, device_unplugged, this);
}
#endif

/* Calculate the final parameters for this audio specification */
SDL_CalculateAudioSpec(&this->spec);
Expand Down Expand Up @@ -779,6 +817,7 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
numAudioBuffers = ((int)SDL_ceil(MINIMUM_AUDIO_BUFFER_TIME_MS / msecs) * 2);
}

this->hidden->numAudioBuffers = numAudioBuffers;
this->hidden->audioBuffer = SDL_calloc(1, sizeof (AudioQueueBufferRef) * numAudioBuffers);
if (this->hidden->audioBuffer == NULL) {
SDL_OutOfMemory();
Expand All @@ -794,6 +833,7 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
CHECK_RESULT("AudioQueueAllocateBuffer");
SDL_memset(this->hidden->audioBuffer[i]->mAudioData, this->spec.silence, this->hidden->audioBuffer[i]->mAudioDataBytesCapacity);
this->hidden->audioBuffer[i]->mAudioDataByteSize = this->hidden->audioBuffer[i]->mAudioDataBytesCapacity;
/* !!! FIXME: should we use AudioQueueEnqueueBufferWithParameters and specify all frames be "trimmed" so these are immediately ready to refill with SDL callback data? */
result = AudioQueueEnqueueBuffer(this->hidden->audioQueue, this->hidden->audioBuffer[i], 0, NULL);
CHECK_RESULT("AudioQueueEnqueueBuffer");
}
Expand All @@ -809,6 +849,20 @@ static BOOL update_audio_session(_THIS, SDL_bool open)
audioqueue_thread(void *arg)
{
SDL_AudioDevice *this = (SDL_AudioDevice *) arg;

#if MACOSX_COREAUDIO
const AudioObjectPropertyAddress default_device_address = {
this->iscapture ? kAudioHardwarePropertyDefaultInputDevice : kAudioHardwarePropertyDefaultOutputDevice,
kAudioObjectPropertyScopeGlobal,
kAudioObjectPropertyElementMaster
};

if (this->handle == NULL) { /* opened the default device? Register to know if the user picks a new default. */
/* we don't care if this fails; we just won't change to new default devices, but we still otherwise function in this case. */
AudioObjectAddPropertyListener(kAudioObjectSystemObject, &default_device_address, default_device_changed, this);
}
#endif

const int rc = prepare_audioqueue(this);
if (!rc) {
this->hidden->thread_error = SDL_strdup(SDL_GetError());
Expand All @@ -820,15 +874,50 @@ static BOOL update_audio_session(_THIS, SDL_bool open)

/* init was successful, alert parent thread and start running... */
SDL_SemPost(this->hidden->ready_semaphore);

while (!SDL_AtomicGet(&this->hidden->shutdown)) {
CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0.10, 1);

#if MACOSX_COREAUDIO
if ((this->handle == NULL) && SDL_AtomicGet(&this->hidden->device_change_flag)) {
SDL_AtomicSet(&this->hidden->device_change_flag, 0);

#if DEBUG_COREAUDIO
printf("COREAUDIO: audioqueue_thread is trying to switch to new default device!\n");
#endif

/* if any of this fails, there's not much to do but wait to see if the user gives up
and quits (flagging the audioqueue for shutdown), or toggles to some other system
output device (in which case we'll try again). */
const AudioDeviceID prev_devid = this->hidden->deviceID;
if (prepare_device(this, this->handle, this->iscapture) && (prev_devid != this->hidden->deviceID)) {
AudioQueueStop(this->hidden->audioQueue, 1);
if (assign_device_to_audioqueue(this)) {
int i;
for (i = 0; i < this->hidden->numAudioBuffers; i++) {
SDL_memset(this->hidden->audioBuffer[i]->mAudioData, this->spec.silence, this->hidden->audioBuffer[i]->mAudioDataBytesCapacity);
/* !!! FIXME: should we use AudioQueueEnqueueBufferWithParameters and specify all frames be "trimmed" so these are immediately ready to refill with SDL callback data? */
AudioQueueEnqueueBuffer(this->hidden->audioQueue, this->hidden->audioBuffer[i], 0, NULL);
}
AudioQueueStart(this->hidden->audioQueue, NULL);
}
}
}
#endif
}

if (!this->iscapture) { /* Drain off any pending playback. */
const CFTimeInterval secs = (((this->spec.size / (SDL_AUDIO_BITSIZE(this->spec.format) / 8)) / this->spec.channels) / ((CFTimeInterval) this->spec.freq)) * 2.0;
CFRunLoopRunInMode(kCFRunLoopDefaultMode, secs, 0);
}

#if MACOSX_COREAUDIO
if (this->handle == NULL) {
/* we don't care if this fails; we just won't change to new default devices, but we still otherwise function in this case. */
AudioObjectRemovePropertyListener(kAudioObjectSystemObject, &default_device_address, default_device_changed, this);
}
#endif

return 0;
}

Expand Down

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